Lets talk about maneuvering speed

FORANE

FORANE

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FORANE
What makes you slow to VA?
If its bumpy do you just avoid full flight control deflection and keep on going at normal cruise speed? Just stay out of the yellow arc when bumpy? only slow to VA in severe turbulence?
 
Mark (midlifeflyer) wrote a good explanation about it.
 
I slow down in bad turbulence. It's a no brainer. <pun intended>
 
I just listened to a podcast about maneuvering speed. Talks about how its calculated and how it isn't a magical number. Podcast is called Direct To and the Episode is #5 "What you didn't know about maneuvering speed". Free and fun listening!
 
Wasn't there a brutal lesson learned in NY, IRT Va, in an airliner?
 
I'm sure I'm a wimp... but any detectable bounce and I'm slowing for the green arc. Heck... 150Kts will get me there, right?
 
rolivi said:
I'm sure I'm a wimp... but any detectable bounce and I'm slowing for the green arc. Heck... 150Kts will get me there, right?
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The green arc is Vno, not Va. Va is generally much slower, particularly if you're light.

My own rule is that physical discomfort means to slow down. Whacking your head is real obvious, but having a queasy passenger is a good one, too.

If things are flying around the cabin and you can't hold airspeed, it's a good idea to slow down and look for smoother air.

A modest chop is not enough to go down to Va, but it sure as heck is good reason to go to Vno.
 
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Granted it is for the bonanza, but this book describes how maneuvering speed is calculated.
http://www.amazon.com/Flying-Beech-Bonanza-John-Eckalbar/dp/0961654430

If memory serves, it is a point between the wings popping off (too fast) and the wings stalling (too slow). This is after the gusts associated with turbulence is calculated.

Yes, Eckalbar explains it way better.
 
FORANE said:
What makes you slow to VA?
If its bumpy do you just avoid full flight control deflection and keep on going at normal cruise speed? Just stay out of the yellow arc when bumpy? only slow to VA in severe turbulence?
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Maneuvering speed is not so much about full flight control deflection as it is about a gust or a wind shear event, especially vertical, being able to to cause wing loading that exceeds the design structural limits of aircraft. This can happen when you are maintaining a perfectly level flight attitude. At maneuvering speed, there is no unstalled AOA that can load the wing above its design limits. Maneuvering speed is slightly less than 2x stall speed in the current configuration and weight.
 
Va is typically significantly lower than Vno (top of green arc)

The plane I fly cruises well into the yellow arc. So I slow for Vno when in anything more than very light chop.

Va is 30-40mph under that. I have slowed to Va a few times when in bad turbulence, or when expecting bad turbulence. Flying through a building cumulus cloud etc...
 
Va is a value an airframe manufacturer chooses in order to comply with FAA regs. It doesn't have much to do with anything important and isn't a standard calculation for different manufacturers or models. That's all most of us really know about it. My C-180 Va is 123mph but in rough air I prefer 90 because it jars me less while providing a big margin above stall.
 
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I try not to jerk the controls around to the stops at any speed. Smooth application of control inputs can avoid a lot of problems.
 
Light turb - dont care about my inidcated if i know the forecasted conditions and pireps
Light to Mod turb - im outside the yellow slowing to Va
Mod to Heavy? turb - well below Va
Severe turb - im as slow as safely possible

Descending below the cloud base, im outside the yellow.

My main concern is the peak potential. I dont care to snap a wing... even though itll probably snap my neck too.
 
Stewartb said:
Va is a value an airframe manufacturer chooses in order to comply with FAA regs. It doesn't have much to do with anything important and isn't a standard calculation for different manufacturers or models. That's all most of us really know about it. My C-180 Va is 123mph but in rough air I prefer 90 because it jars me less while providing a big margin above stall.
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LOL. The late Sparky Imeson has a nice explanation on the mountain flying site. He also makes a good point that most published maneuvering speeds are based on power off stall speed but how often do you penetrate turbulence with the engine idling? He recommends using 1.7 X the stall speed at that weight and configuration as your maneuvering speed.

http://www.mountainflying.com/pages/mountain-flying/turb_va.html
 
Sundancer said:
Wasn't there a brutal lesson learned in NY, IRT Va, in an airliner?
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AA587.

Not really a Va lesson as transport jets do not have a published Va. The lesson was more about full control reversals and that lesson would apply to GA aircraft which do have a published Va.
 
Larry in TN said:
AA587.

Not really a Va lesson as transport jets do not have a published Va. The lesson was more about full control reversals and that lesson would apply to GA aircraft which do have a published Va.
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What do you guys do in severe turbulence?
 
Cpt_Kirk said:
Light turb - dont care about my inidcated if i know the forecasted conditions and pireps
Light to Mod turb - im outside the yellow slowing to Va
Mod to Heavy? turb - well below Va
Severe turb - im as slow as safely possible

Descending below the cloud base, im outside the yellow.

My main concern is the peak potential. I dont care to snap a wing... even though itll probably snap my neck too.
Click to expand...

Not sure about your airplane, but often severe turbulence means a write up in the logbook.
 
MAKG1 said:
The green arc is Vno, not Va. Va is generally much slower, particularly if you're light.

My own rule is that physical discomfort means to slow down. Whacking your head is real obvious, but having a queasy passenger is a good one, too.

If things are flying around the cabin and you can't hold airspeed, it's a good idea to slow down and look for smoother air.

A modest chop is not enough to go down to Va, but it sure as heck is good reason to go to Vno.
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This is about how I handle it. Small bumps I just keep it out of the yellow arc. If it's moderate bumps or something that's throwing my heading or altitude off to where the airplane is upset significantly, I'll slow to VA. Realistically I rarely(possibly never) fly in turbulence heavy enough to worry about keeping it at Va.
 
I happen to be watching the Sporty's IR course and just covered the section on turbulence. It included the below statement. To be honest, aerodynamics is not my strong suit. If someone can make sense of this for me, it would be appreciated.

Edit - I do understand the last sentence as a conclusion of the previous two.

"From a structural standpoint, when considering the effects of the vertical gusts only, the best speed to fly in turbulence might be somewhat above maneuvering speed. This is because the increase in wing loading caused by turbulence starts at the leading edge and spreads aft while the increased loads caused by abrupt control movements start at the trailing edge. Because the pilot might move the controls abruptly in turbulence, maneuvering speed has stood the test of time as the target airspeed when the going gets rough."
 
alfadog said:
I happen to be watching the Sporty's IR course and just covered the section on turbulence. It included the below statement. To be honest, aerodynamics is not my strong suit. If someone can make sense of this for me, it would be appreciated.

Edit - I do understand the last sentence as a conclusion of the previous two.

"From a structural standpoint, when considering the effects of the vertical gusts only, the best speed to fly in turbulence might be somewhat above maneuvering speed. This is because the increase in wing loading caused by turbulence starts at the leading edge and spreads aft while the increased loads caused by abrupt control movements start at the trailing edge. Because the pilot might move the controls abruptly in turbulence, maneuvering speed has stood the test of time as the target airspeed when the going gets rough."
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I'm not familiar with the point they are making, but I would guess it is referring to where the force is applied and the result on the lifting surface. If the aerodynamic center is the fulcrum, then in maneuvering flight, the force is applied to the tail which will shift the center of (lift)pressure aft. The trailing edge would essentially be moving down, lowering the pressure at the trailing edge of the airfoil. A gust would apply pressure in front of the aerodynamic center.
That's just a guess, someone smarter on the science of it can give a better answer.
 
Using Va as a turbulent penetration speed doesn't totally protect the plane from structural damage. This is because the protection from structural damage is for a gust that is all in the vertical dimension. Gusts come in all sized and shapes, usually waves of some shape, can be modeled as a spiral. That horizontal component can cause additional stress that isnt going to stall the aircraft, its going to cause the aircraft to encounter MORE horizontal speed, if you will, and acceleration forces. Its so complicated. Suffice to say there are gusts out there that can break up an airplane, mostly in Thunderstorms, even at below Va.
 
Larry in TN said:
AA587.

Not really a Va lesson as transport jets do not have a published Va. The lesson was more about full control reversals and that lesson would apply to GA aircraft which do have a published Va.
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wanna bet? mine does....

its in the limitations section and is a memory item

bob
 
coloradobluesky said:
Using Va as a turbulent penetration speed doesn't totally protect the plane from structural damage. This is because the protection from structural damage is for a gust that is all in the vertical dimension. Gusts come in all sized and shapes, usually waves of some shape, can be modeled as a spiral. That horizontal component can cause additional stress that isnt going to stall the aircraft, its going to cause the aircraft to encounter MORE horizontal speed, if you will, and acceleration forces. Its so complicated. Suffice to say there are gusts out there that can break up an airplane, mostly in Thunderstorms, even at below Va.
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Do you mind elaborating?

The horizontal component isn't considered a factor in exceeding structural limits. It is the vertical component that significantly increases load factor. I'm not quite following what you are saying.
 
Horizontal component increases the airspeed of the airplane because the horizontal component is added. So instead of flying at Va, you are flying at Va plus the horizontal component of the gust, when it hits.
 
coloradobluesky said:
Horizontal component increases the airspeed of the airplane because the horizontal component is added. So instead of flying at Va, you are flying at Va plus the horizontal component of the gust, when it hits.
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Ok, but a gust is going to have a horizontal and vertical component, and the aircraft will only encounter one gust at a time. If the horizontal component is such that it increases airspeed, the vertical component will be diminished. In calculating gust loads, the horizontal component is considered insignificant.
 
Cooter143 said:
Ok, but a gust is going to have a horizontal and vertical component, and the aircraft will only encounter one gust at a time. If the horizontal component is such that it increases airspeed, the vertical component will be diminished. In calculating gust loads, the horizontal component is considered insignificant.
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Ever seen two water waves crash into each other from opposite directions? Air can certainly do the same thing. The assumption an aircraft will "only encounter one gust at a time" seems inaccurate to me.
 
denverpilot said:
Ever seen two water waves crash into each other from opposite directions? Air can certainly do the same thing. The assumption an aircraft will "only encounter one gust at a time" seems inaccurate to me.
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To be accurate, your example would have to reference underwater currents on a submarine or something else submerged, not wave action on the surface. The point is, gust forces will be reduced to a resultant vector acting upon the wing structure. That vector can shift, but when considering wing loading and structural limits the vertical component is what will significantly impact the aircraft. Any other direction will not increase lift significantly, which in turn will not increase load factor significantly.

Edit: I get what CBS is saying, and the difference is theoretical/practical. The bigger issue though, would be asymmetric wing loading. Maneuvering speed is built off of symmetric when loading, whereas turbulence penetration speed should consider asymmetric forces.
 
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Cooter143 said:
Ok, but a gust is going to have a horizontal and vertical component, and the aircraft will only encounter one gust at a time. If the horizontal component is such that it increases airspeed, the vertical component will be diminished. In calculating gust loads, the horizontal component is considered insignificant.
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No, he has a valid point. However, you cannot design for every eventuality and you do want to fly at a speed that will get you through the turbulence expeditiously without stalling the wing at every vertical gust.
 
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